fix: MCP toolset resolution for runtime and config (#3252)

Gateway sessions had their own inline toolset resolution that only read
platform_toolsets from config, which never includes MCP server names.
MCP tools were discovered and registered but invisible to the model.

- Replace duplicated gateway toolset resolution in _run_agent() and
  _run_background_task() with calls to the shared _get_platform_tools()
- Extend _get_platform_tools() to include globally enabled MCP servers
  at runtime (include_default_mcp_servers=True), while config-editing
  flows use include_default_mcp_servers=False to avoid persisting
  implicit MCP defaults into platform_toolsets
- Add homeassistant to PLATFORMS dict (was missing, caused KeyError)
- Fix CLI entry point to use _get_platform_tools() as well, so MCP
  tools are visible in CLI mode too
- Remove redundant platform_key reassignment in _run_background_task

Co-authored-by: kshitijk4poor <kshitijk4poor@users.noreply.github.com>

tests/gateway/test_reasoning_command.py

@@ -218,3 +218,112 @@ class TestReasoningCommand:
         assert result["final_response"] == "ok"
         assert _CapturingAgent.last_init is not None
         assert _CapturingAgent.last_init["reasoning_config"] == {"enabled": False}
+
+    def test_run_agent_includes_enabled_mcp_servers_in_gateway_toolsets(self, tmp_path, monkeypatch):
+        hermes_home = tmp_path / "hermes"
+        hermes_home.mkdir()
+        (hermes_home / "config.yaml").write_text(
+            "platform_toolsets:\n"
+            "  cli: [web, memory]\n"
+            "mcp_servers:\n"
+            "  exa:\n"
+            "    url: https://mcp.exa.ai/mcp\n"
+            "  web-search-prime:\n"
+            "    url: https://api.z.ai/api/mcp/web_search_prime/mcp\n",
+            encoding="utf-8",
+        )
+
+        monkeypatch.setattr(gateway_run, "_hermes_home", hermes_home)
+        monkeypatch.setattr(gateway_run, "_env_path", hermes_home / ".env")
+        monkeypatch.setattr(gateway_run, "load_dotenv", lambda *args, **kwargs: None)
+        monkeypatch.setattr(
+            gateway_run,
+            "_resolve_runtime_agent_kwargs",
+            lambda: {
+                "provider": "openrouter",
+                "api_mode": "chat_completions",
+                "base_url": "https://openrouter.ai/api/v1",
+                "api_key": "test-key",
+            },
+        )
+        fake_run_agent = types.ModuleType("run_agent")
+        fake_run_agent.AIAgent = _CapturingAgent
+        monkeypatch.setitem(sys.modules, "run_agent", fake_run_agent)
+
+        _CapturingAgent.last_init = None
+        runner = _make_runner()
+
+        source = SessionSource(
+            platform=Platform.LOCAL,
+            chat_id="cli",
+            chat_name="CLI",
+            chat_type="dm",
+            user_id="user-1",
+        )
+
+        result = asyncio.run(
+            runner._run_agent(
+                message="ping",
+                context_prompt="",
+                history=[],
+                source=source,
+                session_id="session-1",
+                session_key="agent:main:local:dm",
+            )
+        )
+
+        assert result["final_response"] == "ok"
+        assert _CapturingAgent.last_init is not None
+        enabled_toolsets = set(_CapturingAgent.last_init["enabled_toolsets"])
+        assert "web" in enabled_toolsets
+        assert "memory" in enabled_toolsets
+        assert "exa" in enabled_toolsets
+        assert "web-search-prime" in enabled_toolsets
+
+    def test_run_agent_homeassistant_uses_default_platform_toolset(self, tmp_path, monkeypatch):
+        hermes_home = tmp_path / "hermes"
+        hermes_home.mkdir()
+        (hermes_home / "config.yaml").write_text("", encoding="utf-8")
+
+        monkeypatch.setattr(gateway_run, "_hermes_home", hermes_home)
+        monkeypatch.setattr(gateway_run, "_env_path", hermes_home / ".env")
+        monkeypatch.setattr(gateway_run, "load_dotenv", lambda *args, **kwargs: None)
+        monkeypatch.setattr(
+            gateway_run,
+            "_resolve_runtime_agent_kwargs",
+            lambda: {
+                "provider": "openrouter",
+                "api_mode": "chat_completions",
+                "base_url": "https://openrouter.ai/api/v1",
+                "api_key": "test-key",
+            },
+        )
+        fake_run_agent = types.ModuleType("run_agent")
+        fake_run_agent.AIAgent = _CapturingAgent
+        monkeypatch.setitem(sys.modules, "run_agent", fake_run_agent)
+
+        _CapturingAgent.last_init = None
+        runner = _make_runner()
+
+        source = SessionSource(
+            platform=Platform.HOMEASSISTANT,
+            chat_id="ha",
+            chat_name="Home Assistant",
+            chat_type="dm",
+            user_id="user-1",
+        )
+
+        result = asyncio.run(
+            runner._run_agent(
+                message="ping",
+                context_prompt="",
+                history=[],
+                source=source,
+                session_id="session-1",
+                session_key="agent:main:homeassistant:dm",
+            )
+        )
+
+        assert result["final_response"] == "ok"
+        assert _CapturingAgent.last_init is not None
+        assert "homeassistant" in set(_CapturingAgent.last_init["enabled_toolsets"])

tests/hermes_cli/test_tools_config.py

@@ -35,6 +35,39 @@ def test_platform_toolset_summary_uses_explicit_platform_list():
     assert summary["cli"] == _get_platform_tools(config, "cli")
 
 
+def test_get_platform_tools_includes_enabled_mcp_servers_by_default():
+    config = {
+        "mcp_servers": {
+            "exa": {"url": "https://mcp.exa.ai/mcp"},
+            "web-search-prime": {"url": "https://api.z.ai/api/mcp/web_search_prime/mcp"},
+            "disabled-server": {"url": "https://example.com/mcp", "enabled": False},
+        }
+    }
+
+    enabled = _get_platform_tools(config, "cli")
+
+    assert "exa" in enabled
+    assert "web-search-prime" in enabled
+    assert "disabled-server" not in enabled
+
+
+def test_get_platform_tools_keeps_enabled_mcp_servers_with_explicit_builtin_selection():
+    config = {
+        "platform_toolsets": {"cli": ["web", "memory"]},
+        "mcp_servers": {
+            "exa": {"url": "https://mcp.exa.ai/mcp"},
+            "web-search-prime": {"url": "https://api.z.ai/api/mcp/web_search_prime/mcp"},
+        },
+    }
+
+    enabled = _get_platform_tools(config, "cli")
+
+    assert "web" in enabled
+    assert "memory" in enabled
+    assert "exa" in enabled
+    assert "web-search-prime" in enabled
+
+
 def test_toolset_has_keys_for_vision_accepts_codex_auth(tmp_path, monkeypatch):
     monkeypatch.setenv("HERMES_HOME", str(tmp_path))
     (tmp_path / "auth.json").write_text(

tests/hermes_cli/test_tools_disable_enable.py

@@ -134,6 +134,23 @@ class TestToolsMixedTargets:
         assert "web" not in saved["platform_toolsets"]["cli"]
         assert "create_issue" in saved["mcp_servers"]["github"]["tools"]["exclude"]
 
+    def test_builtin_toggle_does_not_persist_implicit_mcp_defaults(self):
+        config = {
+            "platform_toolsets": {"cli": ["web", "memory"]},
+            "mcp_servers": {"exa": {"url": "https://mcp.exa.ai/mcp"}},
+        }
+        with patch("hermes_cli.tools_config.load_config", return_value=config), \
+             patch("hermes_cli.tools_config.save_config") as mock_save:
+            tools_disable_enable_command(Namespace(
+                tools_action="disable",
+                names=["web"],
+                platform="cli",
+            ))
+        saved = mock_save.call_args[0][0]
+        assert "web" not in saved["platform_toolsets"]["cli"]
+        assert "memory" in saved["platform_toolsets"]["cli"]
+        assert "exa" not in saved["platform_toolsets"]["cli"]
+
 
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